1. Technical Field
The present invention relates to the structure of an electro-optical device that includes an electro-optical panel and a light-transmissive member that overlaps the electro-optical panel when viewed in plan, though not limited thereto.
2. Related Art
An electro-optical device is used in a variety of electronic apparatuses such as a mobile phone, a personal digital assistance, and the like for the purpose of displaying video information such as images.
An example of such an electro-optical device is a liquid crystal display device that is provided with a liquid crystal display panel, which is made up of a pair of substrates and liquid crystal that is sandwiched and sealed between the pair of substrates. A liquid crystal display panel is vulnerable to an external force such as a pressing force, a shock, and the like that is applied from the outside. In order to protect a weak liquid crystal display panel against an external force, a transparent protection cover is provided at the image-display side of the liquid crystal display panel. If a layer of air exists between the transparent protection cover and the liquid crystal display panel in such a configuration, light is diffused due to a difference in the index of refraction between these media, which results in degradation in display quality.
An image display device that can prevent such degradation in display quality from occurring is disclosed in JP-A-2006-290960. In the configuration of an image display device that is described in JP-A-2006-290960, a light-transmissive adhesion sheet that is made of a transparent gel having a predetermined gel pattern is provided between the liquid crystal display panel and the transparent protection cover. By this means, it is possible to achieve high shock absorption property without decreasing visual performance. In addition, techniques that are related to the art explained above are described in JP-A-2004-101636 and JP-A-2004-272059.
In a typical configuration of an electro-optical device of related art, a black pattern is printed at a peripheral edge part on one surface of the transparent protection cover that faces toward the liquid crystal display panel and/or is closer to the liquid crystal display panel than the other opposite surface thereof. Specifically, the black pattern is provided for preventing the leakage of a beam of light coming from a side at which the liquid crystal display panel is provided. The one surface mentioned above may be hereafter referred to as liquid-crystal-display-panel-side surface. The side at which the liquid crystal display panel is provided may be hereafter referred to as liquid-crystal-display-panel side. The black pattern has a single-layer structure. The black pattern is formed as a film layer that is thin enough so as not to allow optical leakage. Since the black pattern is formed as a thin layer, a difference in level between the surface of the transparent protection cover at an area at which the black pattern is printed and the surface thereof at an area at which the black pattern is not printed is small. In addition, the light-transmissive adhesion sheet is made of a material that can be elastically deformed and has shock-absorbing property. Because of the structure explained above, there is almost no possibility that air bubbles, which cause degradation in display quality, are produced at the level-difference area part when the transparent protection cover is bonded to the light-transmissive adhesion sheet that has been pre-bonded to a bonding surface of the liquid crystal display panel or when the light-transmissive adhesion sheet is bonded to the transparent protection cover before it is bonded to the bonding surface of the liquid crystal display panel.
In order to make the design of a transparent protection cover more sophisticated, these days, there is a demand for a light-color printed pattern that is not the black printed pattern at a peripheral edge part on the liquid-crystal-display-panel-side surface of the transparent protection cover. However, if such a light-color printed pattern is adopted, inner components provided at the liquid-crystal-display-panel side may be seen through when observed from the peripheral edge part of the transparent protection cover, which is not desirable. In order to prevent the inner components provided at the liquid-crystal-display-panel side from being seen through, it is necessary to form a dark-color pattern in such a manner that the dark-color pattern overlaps at least a part of the light-color pattern for the shielding of light.
If such a configuration is adopted, overlapping layers that are made up of a design color pattern and a dark pattern, the latter of which is printed so as to overlap at least a part of the former for see-through prevention, are formed. Therefore, a difference in level between the surface of the transparent protection cover at an area at which the dual-layer pattern is printed and the surface thereof at an area at which the pattern is not printed at all is relatively large. Because of such a relatively large level difference, it is more likely that air bubbles are produced at the level-difference area part when the transparent protection cover is bonded to the light-transmissive adhesion sheet that has been pre-bonded to the bonding surface of the liquid crystal display panel or when the light-transmissive adhesion sheet is bonded to the transparent protection cover before it is bonded to the bonding surface of the liquid crystal display panel. In addition, it is difficult to make the air bubbles escape to the outside. If any air bubble remains without being removed at the level-difference area part, there is a risk that display quality is adversely affected due to a difference in the index of refraction of the air bubble and the index of refraction of the light-transmissive adhesion sheet and the like.
Moreover, since a large level difference is formed on the transparent protection cover, a distance between the transparent protection cover and the liquid crystal display panel is also large. Therefore, there is an adverse possibility that a stress is applied to the liquid crystal display panel in a direction of pulling the liquid crystal display panel toward the transparent protection cover due to the adhesion force of the light-transmissive adhesion sheet when the liquid crystal display panel and the transparent protection cover are bonded to each other with the use of the light-transmissive adhesion sheet. In addition, there is an adverse possibility that a stress that causes the liquid crystal display panel to be deflected under the pulling force is applied to the liquid crystal display panel. For this reason, display unevenness or other image problems might occur at the time of the driving of the liquid crystal display panel due to the deflection thereof, which results in degradation in display quality.